Narcissists are one-state machines, programmed to extract Narcissistic Supply from others. To do so, they develop early on a set of immutable routines. This propensity for repetition, this inability to change and rigidity confine the narcissist, stunt his development, and limit his horizons. Add to this his overpowering sense of entitlement, his visceral fear of failure, and his invariable need to both feel unique and be perceived as such - and one often ends up with a recipe for inaction.
The under-achieving narcissist dodges challenges, eludes tests, shirks competition, sidesteps expectations, ducks responsibilities, evades authority - because he is afraid to fail and because doing something everyone else does endangers his sense of uniqueness. Hence the narcissist's apparent 'laziness" and "parasitism". His sense of entitlement - with no commensurate accomplishments or investment - aggravates his milieu. People tend to regard such narcissists as "spoiled brats".
In specious contrast, the over-achieving narcissist seeks challenges and risks, provokes competition, embellishes expectations, aggressively bids for responsibilities and authority and seems to be possessed with an eerie self-confidence. People tend to regard such specimen as "entrepreneurial", "daring", "visionary", or "tyrannical". Yet, these narcissists too are mortified by potential failure, driven by a strong conviction of entitlement, and strive to be unique and be perceived as such.
Their hyperactivity is merely the flip side of the under-achiever's inactivity: it is as fallacious and as empty and as doomed to miscarriage and disgrace. It is often sterile or illusory, all smoke and mirrors rather than substance. The precarious "achievements" of such narcissists invariably unravel. They often act outside the law or social norms. Their industriousness, workaholism, ambition, and commitment are intended to disguise their essential inability to produce and build. Theirs is a whistle in the dark, a pretension, a Potemkin life, all make-belief and thunder.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 2 DVDs with 12 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)